-2 question

[CNW 6000]

I think I know that the -2 upgrade on EMDs is related to traction and fuel management issues that the original engine was blessed with.  My question is would the upgrade have the same effect from SD40 to SD40-2 as the SD70 to SD70M-2 or something along those lines?  Thanks in advance!

[CShaveRR]

Probably the biggest internal change in the Dash Two locomotives of 1972 (never mind the cab roof, sight glass, battery box cover, or added length--those are primarily cosmetic) was the replacement of wired electrical systems with replaceable modules.  This was a large factor in making these and subsequent units easier to troubleshoot and repair.  The horsepower (and, one assumes, the engine itself) was unchanged.

The SD70M-2 is a little more involved:  it's the result of a requirement that emissions be cleaned up to a certain level ("Tier 2"); it has 4300 horsepower vs. 4000 in the SD70.  The rear of the unit, with enlarged radiators, is a prominent spotting difference.

[Lord Atmo]

SD90 series diesels have the same large radiators though. the best way to tell an ACE/M-2 apart from the later SD90 design is the cab. the SD90s had whisper cabs. ACEs dont

[beaulieu]

SD90 series diesels have the same large radiators though. the best way to tell an ACE/M-2 apart from the later SD90 design is the cab. the SD90s had whisper cabs. ACEs dont

The radiator is shorter than the one on the SD90MACs, and the electrical cabinet behind the cab is different meaning the hood is different than the SD90MAC as well.

The last order for SD70ACes for BHP in Australia were built with Isolated cabs, so they may make a comeback in the US on future orders. Most crews feel that the new GEVOs are quieter than the new EMDs.